GER 3568G - Dry Low NOx Combustion Systems for ... - GE Energy

Dry Low NO x Combustion Systems for GE Heavy-Duty Gas Turbines
approximately 70–100% of natural gas while
still maintaining low emissions.
To meet these requirements an updated version
of the DLN-2, called the DLN-2+, was developed.
The DLN-2+ retains the basic architecture
of the DLN-2 with adaptations for both the
new requirements and to improve the operability
and robustness of the existing system. In
comparison to the DLN-2, the major changes
are concentrated in the fuel nozzle and endcover
arrangement (See Figure 28). Both the
endcover and fuel nozzle have substantially
enlarged fuel passages for the increased volumetric
flow of fuel. In addition the fuel nozzle
(See Figure 29), was redesigned for further
improvements in flame holding margin,
reduced pressure drop, and improved diffusion-flame
stability.
The additional gains in flame-holding velocity
margin result from cleaner aerodynamics in the
premixers. This is achieved via a new swirler
design, which incorporates fuel injection directly
from the swirler surface. Each swirler vane
comprises a turning vane and an upstream
straight section. The straight section is hollow
and houses the fuel manifolds plus the discrete
injection holes. Upstream of the swirler an inlet
flow conditioner improves the character of the
flow entering the premixer, while downstream
an integral outer shroud eliminates any poten-
Figure 28. Parts highly modified for DLN-2+ as
compared to DLN-2
Figure 29. DLN-2+ fuel nozzle
tial flow disturbances after the point of fuel
injection. The improvement in aerodynamics
also reduces the overall system pressure drop to
the level required by the new cycle.
The nozzle-tip geometry and the improvements
in diffusion flame stability allow the use of a diffusion
flame on every nozzle. This eliminates
the lean-lean mode of the DLN-2 and results in
the simplified staging methodology shown in
Figure 30.
A further simplification illustrated in Figure 30 is
the elimination of the DLN-2 Quaternary fuel
system. This is achieved through the use of biradial
fuel staging in each swirler vane. In this
design the radial fuel injection balance can be
adjusted via fixed orifices on the endcover as
part of the system setup procedure.
Overall, the fuel nozzle and endcover arrangement
of the DLN-2+ can accept fuels with
Wobbe Index ranging from 28 to 52. The fuel
GE Power Systems ■ GER-3568G ■ (10/00) 15
PM4
4
4
1
4
4
PM1
D5 - Diffusion Flame on All
PM4 - Premixed Flame on “4”
PM1 - Premixed Flame on “1”
D5
D5
D5 + PM1 + PM4
PM1 + PM4
IGNITION to
LOW LOAD
LOW LOAD to
PREMIX TRANSFER
PREMIX TRANSFER
to BASE LOAD
Premix Dynamics Control: PM4/PM1 Fuel Split
Load Reject to Underlined Mode
Figure 30. DLN-2+ staging methodology